1. Field of the Art
This invention relates to construction of an endoscopic light source connector for connecting a light guide of an endoscope to a light source, to transmit illumination light to a subject under endoscopic observation, the light source connector having a plug portion which is provided on the side of the endoscopic light guide and a socket portion which is provided on the side of a casing of the light source which houses a source lamp.
2. Prior Art
Endoscopes which are in use in medical fields are generally constituted by an insertion instrument which is extended out on the front side of a manipulating head assembly, and a universal cable which is led out on the rear side of the manipulating head assembly in the opposite direction away from the insertion instrument. The universal cable is provided with a light source connector at its proximal end to be disconnectibly connected to an illumination light source device having an illumination lamp housed in a casing. For this purpose, a socket portion is provided on the side of the light source casing.
In use, usually an endoscope of a suitable construction is selected depending upon the operator's taste or familiarity. Alternatively, an endoscope of a particular type is used depending upon the purpose of use or depending upon the nature of an endoscopic examination to be conducted. On the other hand, a light source to be installed in an endoscopic examination room is desirably arranged to permit connection of endoscopes of different types. One and single light source can be used for various types of endoscopes if plug portions on the respective endoscopes are constructed to common dimensional specifications. For instance, in the case of Japanese Laid-Open Patent Application S58-152532, light source connectors of different constructions are connected to a socket portion of one light source by the use of an adaptor.
In order to ensure smooth painless introduction into a body cavity, it is a paramount requisite for an endoscopic insertion instrument to be as small as possible in diameter or thickness. The same applies to a light guide to be threaded through the insertion instrument. In order to transmit a sufficient amount of light through a narrow light guide, it is necessary for a light source to employ a source lamp which can emit a large quantity of light, for example, a high intensity lamp like a xenon lamp. However, use of a xenon lamp involves a number of problems. For example, it requires an exclusive starting device, in addition to the difficulties that it is costly and necessitate to provide a light source which is larger in construction as a whole. For these reasons, there has been a trend toward employing a simpler halogen lamp as an endoscopic light source. As compared with a xenon lamp, a halogen lamp is lower in light intensity. Therefore, in the case of a light source with a low intensity lamp, it becomes necessary to enhance light condensing efficiency by using a light guide of a larger diameter.
As described above, high intensity lamps as well as low intensity lamps have been employed as a source lamp in various endoscopic light sources. In this regard, it is not desirable to connect a narrow light guide to a light source with a low intensity lamp because it will result in an insufficient illumination light level. In this regard, it is possible to connect a thick light guide to a high intensity lamp. However, transmission of illumination light in an excessively large volume can result in halation of endoscopic images because a solid-state image sensor device is likely to be saturated with increased light reflections off intracavitary walls, in addition to a problem of increased heat radiation toward the intracavitary wall. These problems can be eliminated to a certain degree by lowering the light intensity or by using a filter or the like. Accordingly, it is not impossible to connect an endoscope with a light guide of a relatively large diameter to a light source having a high intensity lamp.
The plug portion on the side of the light guide to be disconnectibly connected to a socket portion on a light source casing is arranged into a rod-like shape which is generally referred to as “light guide rod.” In some cases, for the purpose of facilitating connections and disconnections, the light guide rod is arranged to be lightly connected with the socket portion at the sacrifice of the stability of the light guide rod in the connected state. Besides, usually a light guide rod is projected out of a light source connector casing, and the light guide rod is arranged to protrude largely into a light source through a coupling portion in a socket portion. Therefore, there are possibilities of the plugged end of the light guide rod being put in quaking movements when the universal cable is pulled taut or when the casing of the light source is vibrated.
As the light source connector is plugged into the socket, the light guide rod is brought into alignment with the optical axis of an illumination light path from the source lamp. However, if the light guide rod is put in a vibrating movement, flickering of illumination light or variations in illumination light level occur due to repeated deviations of the light guide rod from the optical axis of the light source. Therefore, it is desirable to provide on the side of the light source a centering mechanism with a rod end holder for fixedly holding a tip end portion of the light guide rod in an aligned position, for example, as disclosed in Japanese Laid-Open Utility Model Application H3-26491.
Thick and narrow light guide rods conspicuously differ from each other in diameter. Therefore, in making it possible to connect two different types of light guide rods to one common light source, it becomes necessary for the light source to employ a centering mechanism with a rod end holder which is capable of holding both thick and narrow light guide rods in an aligned center position despite differences in diameter.